I was reading about St. Nicholas who helped in part inspire our modern stories of Santa Claus and read the following:

One weak tradition has him actually attending the Council of Nicea in A.D. 325, when Arian doctrine was rejected. The story goes that he got into a heated debate with Arius himself about whether there was a time when the Word did not exist. Nicholas strongly disagreed.

The debate ended suddenly when Nicholas punched out Arius then and there on the floor of the council!

There's no source listed for the "weak tradition" and it certainly makes a very interesting story especially if true. Typically the saint is the victim. Where did the story originate and how old is it? What is the likelihood that it's actually true? As a side note, was mild violence such as this common in any of the councils that have been held over the centuries?